Insofar as we are aware, the prior art in cap lamps is largely limited to the incandescent bulb type, commonly worn by persons working underground in mines. Standard lamps of this type consume about 4 watts of power and produce about 50 lumens projected like a flashlight in a narrow beam. In an attempt to enlarge the beam size, such lamps have been defocused so that the spot size diverges to a larger ring, but the light intensity then becomes lower.
In the black regions of a coal mine with wall emisitivity ranging from 1 to 4 percent, considerably more light is required to work safely. Roof bolts projecting down from the ceiling, trolley tracks and holes in the floor, pillars, roof support posts, and the myriad obstructions in coal mines are difficult to see with the present cap lamp, and the miner is required to continually move his head in a scanning fashion to identify obstructions which could be hazardous. Although these problems are commonly known in mining operations, similar problems are also present in other operations, such as in construction, service and the like.
In our improved fluorescent lamp construction, the lamp operates at a power level of about 4 watts, but the light output is approximately 300 lumens. Although the light does not focus in a narrow spot, the great increase in light output, as compared with the incandescent bulb type, makes this a significant improvement in visability and, therefore, safety for the workman. Because of the lateral length of the fluorescent lamp, and the reflector associated therewith, the resulting light pattern is horizontal and quite wide, so that the workman may easily view a fairly wide expanse in front of him, without moving his head side-to-side or up and down.